Not proud of this pic, more of a warning, please be aware where the onlookers are at all times. One busy trying to take a pic of my landing, had to abort and go around. All of them went to the side when I landed the next time, they were a very fantastic group and enjoyed every moment. Just be careful please.

It always surprises me how many people don't know about or follow AMA rules about flying near bystanders. Though it seems innocent enough, the physics of a 1 lb model airplane even when moving slowly, and even if made from foam can, and has caused severe injuries if they hit someone, (not to mention propellers spinning at high rpm). I've seen guys do near 100 mph passes right over people's heads with edf's; a disaster waiting to happen.

if you use Mass X Velocity, a one pound weight at 100 MPH would have the momentum of 100 lbs force. staggering when you think about it. reminds me of Sherlock buzzing that dog walkers head at the park. jeez.

if you use Mass X Velocity, a one pound weight at 100 MPH would have the momentum of 100 lbs force. staggering when you think about it. reminds me of Sherlock buzzing that dog walkers head at the park. jeez.

Well said, I've been in modeling since the 60's, and have seen some very severe injuries, especially from prop strikes on standers-by, and am a long-time proponent of the AMA and it's standards. An edf at high velocity can be a very dangerous weapon if flown irresponsibly, that's why the AMA created safety rules. Those that ignore those rules endanger all of the sport and tarnish it's image.

I am a sailplane pilot and competitor, though I also fly edf's. Even a glider can do damage, and in fact I've seen injuries from a person being struck by an out of control sailplane on more than one occasion. Physics dictate everything about our flying machines, and mass + velocity can injure at any time.

do the math. a 3 lb glider flying at 300MPH = 900 lbs of momentum. if you want to go even further, you could crunch the numbers to find out how much weight that puts per square inch at impact and also how many G's it would produce. the numbers are staggering and there's several people on this forum that just don't get it. they could get smacked in the head with it and they still wouldn't get it. LOL.

Back in the 80's I went to a soaring contest at the park next to the Rose Bowl, one of the locals, (a kid), was goofing around with a straight-winged 2M sailplane doing aerobatics and generally showing off. He did several fast dives towards a crowd of onlookers as a joke, but on one dive didn't pull out in time and hit a guy on the head with the wingtip of his plane and opened him up like a melon; he got a concussion and 30 stitches because of it. Back in the 60's I watched a friend tuning his .29 nitro engine on a free flight while holding the fuselage with his left hand, reached under the wing with his right to tweak the needle valve when a gust of wind came up and blew the wing, engine running at full tilt up into his face; the prop started at his nose and worked it's way up his forehead before he dropped it; whole thing took about 1 second beginning to end. My dad and I had to transport him 30 miles to the hospital in our car with a 10 yr old me holding a towel on his head, (bloody mess, no cell phones to call for help back then; had nightmares about it). He went through several plastic surgeries and several hundred stitches to fix that one and was pretty much scarred for life. Last year a girl at a park in Florida got mangled by a nitro helicopter: http://www.rcgroups.com/forums/showt...+by+helicopter . Something seemingly innocent and fun can turn to disaster very quickly if safety protocols are ignored, and from the vids I've seen that happens much more than it should. I fully support AMA's Safety Code, wish everyone did.

when I learned to fly back in the early 80's (in the UK), our club was at a Rugby field. we had to avoid goal poststrees, buildings, you name it. LOL. I've seen more than enough flat spins than I could ever count, after hitting the verticals of the goal. I've seen people get hit (and worse) and the worst/best I ever saw, was a large nitro, cleave (for lack of a better word) a very nice, large hole in the roof of a car. of course, the rest of the roof was dented in from the rest of the plane hitting it, but I'll never forget the new, designer hole in the roof of that car.

Take the voltaje of the battery and multiply the Kv of the motor = fan RPM.
11.1V x 3600= 39,960.

A reality more about:

3 cell lipo, have a voltage of approximately 12.6Volts.
The new batteries 30 and 20 C 40C sustain discharge voltage 11V average. (Use the voltage rating is very rough and correct)

A very important factor that is missing from this equation is the NLS% (percentage of No Load Speed.)
In EDF is very important that the engine is not charged too much for this factor does not drop below 80%. Possibly in some applications where the motor is much torture can be used up to 75%. But it is highly not recommended.

Also consider the actual motor Kv can vary the die post for the manufacturer.

Take the voltaje of the battery and multiply the Kv of the motor and multiply for %NLS factor = fan RPM.
11.1V x 3600 x 80%= 31,968 RPM.

To Calculate what Kv motor you need:
Take the desired fan RPM, divide it by the battery voltaje = Need ed motor Kv.

Once you factor% but the NLS was ignored the formula would be:
45,000 / (3600 * 80%) = 15.62V (can not say they are 4 cell)
It is impossible to change the voltages of the Lipo. Will always be multiples of 3.7.
So we have to recalculate to 4 or 5 cells. To calculate the Kv busy, since it is the only viable option we have, change the engine to the appropriate one.

As a completely green newbie to the hobby, EDF jets interested me after reading about them and watching the videos.

This thread has really helped me to realize what I could be up against. I really look forward to getting one and building it, but flying it would be a different matter without some major practice with a lower-powered plane, first.

Swung by a field in Niagara Falls and watched a couple of guys flying their glow-engined planes(MASSIVE suckers) and spoke with them a bit, one wasn't too keen on EDF, the other owned one and said they're a blast. Good to see the personal stories regarding experiences too.

Here is a video of my first EDF flight earlier this summer. Yes I made big glaring mistakes and it ended up ugly. Live and learn. I'm some what an epoxy expert now after 3 years in the hobby. I can tell you ducted fans get battle scars faster than WWII warbirds do in my case!